The invention relates generally to protective materials and more particularly to water repellant, i.e., waterproofing, membranes which may be applied to the outside of structures, for example, roofs to secure the interior from rain damage.
Waterproofing membranes can be used in any application where it is desirable to protect a substrate from water. For example, waterproofing membranes can be used in water tanks, canals, foundations, patios, landfills and the like. A major use of waterproofing membranes is in the roofing industry. Waterproofing membrane type roofing, also known as single ply roofing, is typically used in construction where roofing structures will accommodate nothing heavier than a single ply installation.
Waterproofing membranes, as typically manufactured, consist of a web of tough, fibrous matting usually of polyester or fiberglass, which is saturated with a waterproofing coating of thermoplastic bituminous material. The process generally consists of saturating the matting with a heated bituminous waterproofing compound in a vat, then immediately cooling and solidifying the bituminous compound in water. This results in a waterproofing membrane having a thick upper surface of waterproofing compound and a thin lower surface of waterproofing compound, i.e., the matting is positioned closer to the lower surface of the membrane. Typically, the upper surface of the membrane is covered with a material such as aluminum sheeting or sand to cover surface defects in the membrane surface and to protect the membrane, for example, from UV radiation which can deteriorate the membrane.
Waterproofing membranes are typically attached to a substrate by heating the membrane, for example, by torch, so as to cause the waterproofing component of the membrane to become slightly molten and flow to bond the membrane to a substrate. In a typical application procedure, the exposed underside of a rolled-up membrane is heated by torch and then unrolled onto the substrate.
However, because of the prior manufacturing techniques employed in producing waterproofing membranes of this type several disadvantages result. A major disadvantage is the difficulty in locating the matting in a pre-determined position within the membrane. As noted, in prior manufacturing methods the matting is located closer to the lower surface of the membrane. Additionally, only the upper surface of the membrane is treated with protective materials. This results in producing a membrane having the protective materials on the thick side of the membrane. Consequently, when the waterproofing membrane is installed, the thin lower surface closest to the matting must be heated. As a result, when the waterproofing membrane is applied to a substrate, the heating can damage the inner matting thus compromising the waterproofing integrity of the membrane. In addition, less waterproofing compound is available for bonding to the substrate and additional thermoplastic material may have to be applied to complete the bond.
Other manufacturing disadvantages in the waterproofing membrane industry are the presence of holes, blisters, and craters, generally on the lower surface of the membrane, due to the explosion of air or moisture bubbles in the matting, thus increasing the chances of compromising the waterproofing integrity of the membrane. This results from moisture inherent in the matting forming bubbles when subjected to the heat of the waterproofing compound, typically at temperatures of about 190.degree. C. If the bubbles do not explode, blisters remain in the membrane. If they explode, holes and craters appear. In addition, production speed must be low in order to cool membranes sufficiently for further processing and storage, especially where the finished membranes approach thicknesses of 4 and 5 millimeters. Consequently, it has been virtually impossible to produce modified membranes in a single processing with times and costs comparable to the production of plain, i.e., non-coated, membranes. Additionally, residual moisture which remains after cooling can be entrapped by additional layers of material applied to the membrane. As a result, separation can occur between the membrane and the applied material. This is especially critical where residual moisture retained by the membrane can cause overlapping seams of the installed membrane to separate.
Because of the disadvantages inherent in prior waterproofing membrane manufacturing methods, an improved process is desired.